Saturable transformer regulator for flyback power supply

Abstract

A flyback type power supply has a nominal 12 volt secondary winding that is connected to a rectifier through the primary winding of a saturable transformer. The secondary winding of the saturable transformer is connected in series with the DC load current supplied by the rectifier. A filter capacitor completes the circuit. Under no load conditions, the impedance presented by the primary of the saturable transformer is high and the output voltage developed across the filter capacitor is maintained at about 12.25 volts. Under full load conditions, the impedance presented is negligible.

What is claimed is: 
     
       1. In combination with a power transformer having a secondary winding; an output filter capacitor;   rectifier means coupled between said secondary winding and said output filter capacitor developing a peak output voltage across said output filter capacitor that rises to undesirable levels under no load conditions; and   saturable transformer means connected between said secondary winding and said rectifier means for automatically compensating for said rise in peak voltage under no load conditions and for imposing minimal voltage drop across said saturable transformer means under full load conditions.   
     
     
       2. The combination of claim 1 wherein said saturable transformer means includes a transformer having a first winding connected between said secondary winding and said redtifier means and a second winding traversed by DC current from said rectifier means. 
     
     
       3. The combination of claim 2 wherein said power transformer is of the flyback type. 
     
     
       4. The combination of claim 3 wherein said rectifier means includes a diode having first and second terminals, and wherein said first winding is connected to said first terminal of said diode and said second winding connected between said second terminal of said diode and said output filter capacitor. 
     
     
       5. A self-regulating flyback transformer power supply comprising: a flyback transformer secondary winding;   a saturable transformer having first and second windings;   a filter capacitor;   a diode having first and second terminals, said first terminal being connected to said secondary winding through said first winding of said saturable transformer and said second terminal being connected to said filter capacitor through said second winding of said saturable transformer.   
     
     
       6. The power supply of claim 5 wherein the inductance of said saturable transformer primary winding is approximately 80 microhenrys under no load conditions and substantially 0 microhenrys under full load conditions.